Thanks for the quick response. I'm pretty sure the sketch is being sent. I have the NG board so i've been pressing reset then sending the sketch to it. I added Serial.println("this is high"); to the statement to see if it was going through the loop properly and it does not print out....am i missing something?

So you're listening to the RPM from a hall effect sensor, but you also want to ouput info to a serial LCD or save info to a USB thumb drive (serial) or send information via wireless (probably serial) to some other device (another arduino?) and you want to listen, or at least post for button inputs because you have a few user inputs... yeah how? How many things can you have interrupts for?

Could you make a simple device to take in the hall effect reading and output an analog signal based on that reading? say at like 1hz reading every second (really slow RPM) vout = 0v and your limit of 100hz vout=5v. You're going to have your "speedometer"

Then Arduino wouldn't really have to listen,but rather post for it. Assuming you don't have any really long loops, you'd probably pick up the vout at least every 100hz... It'd be like a rolling average, but it couldn't ever be too far behind, at least as far as mechanical things go... The problem with hall effect sensors is that they can't really read 0rpm, it has to be assumed.

That's still something I'm having trouble getting my head around as a mechanical guy playing with electrical stuff... 16Mhz is extremely fast for me, 16million operations every second? wow... hard to believe you couldn't pick up something running at 100hz, the issue of course is not if you can pick it up or not, but if you miss the signal, like the hall effect sensor trips when you're not posting for it so you only pick up say 99hz when it's really 100... how much of a difference does it make in the end?

In reality, if you wanted Arduino to collect a lot of data, just how limited are you?

Yeah I'm just sort of thinking out loud, this is something I see myself running into within the next year...